Hypothesis test about µ: small sample, σ unknown, normal population— t-test (Ch. 10-4b) Monthly utility bills factor into local cost of living measures. A group of economists is updating the cost of living index for Delaware. The group believes the mean utility bill has changed over the past year. During the winter of 2015-2016, assume the average monthly utility bill in Delaware was $186. A random sample of 25 residents was selected in the winter of 2016-2017 and the average bill was found to be $177.55, with a sample standard deviation of $22.40. [Assume a normal distribution.]   Test, with 95% confidence, the group’s claim about utility bills.

χ2 confidence interval estimation and test of hypothesis— one variance (Ch. 10-8a & b)

z statistic confidence interval estimation and test of hypothesis—two populations, large samples, σ known, normal population—(Ch. 11-1)